Cholera toxin has been used to label GTP regulatory components associated with fat cell plasma membrane adenylate cyclase. Distinctive labelling patterns are observed, indicating additional components to those found in simpler adenylate cyclase systems. Both the stimulatory (Beta-adrenergic) and inhibitory (adenosine) receptors have also been labelled. In both cases binding is modified by GTP (or Gpp(NH)p). The alfa-adrenergic (inhibitory) receptor from platelet plasma membranes has also been solubilized as a prelude to its insertion in other cell types. Thus, the techniques are now available for a concerted purification of the components of a dually regulated adenylate cyclase system and for a determination of their molecular interactions.